1. Field of the Invention
This invention relates to packaging of semiconductor chips, and in particular various aspects of the present invention relate to a packaged semiconductor device, a combination of a semiconductor chip and a lead frame therefor, a method of manufacturing a semiconductor device, and a mold for molding a resin package around an assembly of a semiconductor chip and a plurality of lead fingers.
2. Description of the Prior Art
There are a number of known manners of manufacturing a semiconductor device, in which a semiconductor chip is sealed in a resin package. FIG. 4 of the accompanying drawings shows a known "die pad" construction in which a chip c is bonded to a die-pad a by a bonding material d, such as a silver paste or a gold-silicon eutectic alloy. The die-pad a is connected to a peripheral portion of a lead frame by connecting fingers a'. A plurality of lead fingers b project from the peripheral portion of the lead frame, and each lead finger b is connected to a respective electrode of the chip c by a respective bonding wire e. The chip c, die-pad a, bonding wires e and inner ends of the fingers a', b are then placed in a molding die and sealed in a resin package.
Another known "chip-on-lead" type of construction is shown in FIG. 5. In this case, an insulator f, such as a polyimide sheet, is placed on the inner ends of lead fingers b, a semiconductor chip c is placed on the insulator f and the electrodes of the semiconductor chip c are connected to respective inner ends of the lead fingers b by respective bonding wires e. Again, the assembly is then sealed in a resin package.
A further known "lead-on-chip" type of construction is shown in FIG. 6. In this case, a surface of a semiconductor chip c, excluding the electrodes thereon, is covered with an insulator f, lead fingers b are placed on the insulator f, and the lead fingers b are connected to respective electrodes by respective bonding wires e. Once again, the assembly is then sealed in a resin package.
Lastly, FIG. 7 shows a known "directly connected" form of construction, in which electrode pads g of a semiconductor chip c project upwardly from the upper surface of the chip c, and the inner ends of lead fingers b are directly connected to the electrode pads g. The assembly is then sealed in a resin package.
It is desirable that the height of the semiconductor device is as small as possible. However, in the die pad construction described above, the thickness of the die pad a and bonding material d add to the height of the package. In the chip-on-lead and lead-on-chip forms of construction described above, the thickness of the insulators f and the lead fingers b add to the height of the package. In the directly connected form of construction described above, the thickness of the lead fingers b and the height of the electrode pads g add to the overall height of the semiconductor package. Also, the die pad construction suffers from the problem that thermal stress is induced in the device due to differences in the coefficients of thermal expansion of the die pad a, the semiconductor chip c and the resin of the package, which can cause a breakdown in bonding between the chip c and the die pad a, between the die pad a and the resin package, or between the chip c and the resin package.